[bugfix] FOUC countermeasures.

examples/inf-primes.html

@@ -6,6 +6,7 @@
     <meta name="description" content="An Online IDE for the Coq Theorem Prover" />
     <link rel="icon" href="../ui-images/favicon.png">
 
+    <style>body { visibility: hidden; } /* FOUC avoidance */</style>
     <link rel="stylesheet" type="text/css" href="../node_modules/bootstrap/dist/css/bootstrap.min.css">
     <link rel="stylesheet" type="text/css" href="../ui-css/landing-page.css">
     <script src="../ui-js/jscoq-loader.js"></script>

index.html

@@ -6,6 +6,7 @@
     <meta name="description" content="An Online IDE for the Coq Theorem Prover" />
     <link rel="icon" href="ui-images/favicon.png">
 
+    <style>body { visibility: hidden; } /* FOUC avoidance */</style>
     <link rel="stylesheet" type="text/css" href="node_modules/bootstrap/dist/css/bootstrap.min.css">
     <script src="node_modules/bootstrap/dist/js/bootstrap.min.js"></script>
     <link rel="stylesheet" type="text/css" href="ui-css/landing-page.css">

ui-css/landing-page.css

@@ -89,3 +89,6 @@ table.doc-actions th, table.doc-actions td {
 table.doc-actions td {
   padding-bottom: .25em;
 }
+
+/* FOUC avoidance */
+body { visibility: visible; }
\ No newline at end of file